Spectrometer module

ABSTRACT

A spectroscopic module includes M beam splitters that are arranged along an X direction, where M is a natural number of 2 or more; M bandpass filters disposed on one side in a Z direction with respect to the M beam splitters, each of the M bandpass filters facing each of the M beam splitters; a light detector disposed on the one side in the Z direction with respect to the M bandpass filters and includes M light receiving regions, each of the M light receiving regions facing each of the M bandpass filters; a first support body supporting the M beam splitters; and a second support body supporting the M bandpass filters. Each of N beam splitters among the M beam splitters has a plate shape and has a thickness of 1 mm or less, where N is a natural number of 2 to M.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 17/137,700, filed Dec. 30, 2020, which claims the benefit of priority to Japanese Patent Application No. 2020-000940, filed Jan. 7, 2020, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a spectroscopic module.

BACKGROUND

As a spectroscopic module that splits measurement light into light in a plurality of wavelength bands to detect the light in each of the wavelength bands, there is known a device in which a plurality of beam splitters and a plurality of bandpass filters are disposed in a casing (for example, refer to Japanese Translation of PCT International Application Publication No. 2013-532293).

SUMMARY

In the spectroscopic module described above, when each of the beam splitters has a plate shape, refraction of light occurs in each of the beam splitters, so that the optical axis of transmitted light is shifted to a side away from the bandpass filter with respect to the optical axis of incident light. For this reason, when the beam splitter is disposed in a rear stage, the optical axis of the incident light is shifted to the side away from the bandpass filter. The amount by which the optical axis of the incident light is shifted is accumulated according to the number of the beam splitters not only on the side away from the bandpass filter but also on a rear stage side in a direction in which the plurality of beam splitters are lined up. For this reason, among a plurality of light receiving regions that detect the light in the plurality of wavelength bands, in a light receiving region other than the light receiving region disposed in the foremost stage, the optical path length of an optical path to the light receiving region is increased depending on the thickness of the beam splitter disposed in a proceeding stage of the beam splitter corresponding to the light receiving region. When the optical path length of the optical path to the light receiving region is increased, the increase leads to a decrease in amount of received light in the light receiving region and the generation of stray light in the optical path, so that the S/N ratio is likely to decrease. Such a phenomenon is more noticeable in the light receiving region disposed in a further rear stage.

An object of the present disclosure is to provide a spectroscopic module of which the S/N ratio can be improved.

According to one aspect of the present disclosure, there is provided a spectroscopic module including: M beam splitters that are arranged along a first direction, where M is a natural number of 2 or more; M bandpass filters that are disposed on one side in a second direction intersecting the first direction with respect to the M beam splitters, each of the M bandpass filters facing each of the M beam splitters; a light detector that is disposed on the one side in the second direction with respect to the M bandpass filters and includes M light receiving regions, each of the M light receiving regions facing each of the M bandpass filters; and a support body that supports the M beam splitters and the M bandpass filters. Each of N beam splitters among the M beam splitters has a plate shape and has a thickness of 1 mm or less, where N is a natural number of 2 to M.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a spectroscopic module of one embodiment.

FIG. 2 is a cross-sectional view along line II-II illustrated in FIG. 1 .

FIG. 3 is a plan view of a portion of a first support body illustrated in FIG. 1 .

FIG. 4 is a cross-sectional view of a portion of a second support body illustrated in FIG. 1 .

FIG. 5 is a cross-sectional view along line V-V illustrated in FIG. 4 .

FIG. 6 is a cross-sectional view along line VI-VI illustrated in FIG. 4 .

FIG. 7 is a view illustrating the dispositional relationship of a plurality of beam splitters with respect to the optical axis of a light incident portion.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. Incidentally, in the drawings, the same or equivalent portions are denoted by the same reference signs, and duplicated descriptions will be omitted.

As illustrated in FIGS. 1 and 2 , a spectroscopic module 1 is a spectrometer module which includes a casing 2, a plurality of beam splitters 3, a plurality of bandpass filters 4, a first support body (support body, support portion) 5, a second support body (support body) 6, a light detector 7, and a light shielding member 8. The plurality of beam splitters 3 are arranged along an X direction (first direction). The plurality of bandpass filters 4 are disposed on one side in a Z direction perpendicular to the X direction (second direction intersecting the first direction) with respect to the plurality of beam splitters 3. The light detector 7 is disposed on the one side in the Z direction with respect to the plurality of bandpass filters 4. The light detector 7 includes a plurality of light receiving regions 7 a.

Each of the beam splitters 3 is, for example, a half mirror, and reflects a part of light, which is incident along the X direction, to the one side in the Z direction and transmits light, which is other than the part of the incident light, to one side in the X direction. Each of the bandpass filters 4 faces each of the beam splitters 3 in the Z direction, and transmit light in a predetermined wavelength band of the light, which is incident from the beam splitters 3 along the Z direction, to the one side in the Z direction. The bandpass filters 4 each transmit light in different wavelength bands. Each of the light receiving regions 7 a faces each of the bandpass filters 4 in the Z direction, and detect the light incident from the bandpass filters 4 along the Z direction. The light receiving regions 7 a form different light detection channels, respectively. In the spectroscopic module 1, measurement light L is split into light in a plurality of wavelength bands by the plurality of beam splitters 3 and the plurality of bandpass filters 4, and the light in each of the wavelength bands is detected by the light detector 7.

As illustrated in FIGS. 1 and 2 , the casing 2 is a housing which accommodates the plurality of beam splitters 3, the plurality of bandpass filters 4, the first support body 5, the second support body 6, the light detector 7, and the light shielding member 8. The casing 2 includes a main body portion 20. The main body portion 20 is formed of a first wall portion 21, a second wall portion 22, a third wall portion 23, and a fourth wall portion 24. The first wall portion 21 and the second wall portion 22 face each other in the X direction. The second wall portion 22 is located on the one side in the X direction with respect to the first wall portion 21. The third wall portion 23 is located on one side in a Y direction perpendicular to both X direction and the Z direction with respect to the first wall portion 21 and the second wall portion 22. The fourth wall portion 24 is located on the other side (side opposite the one side) in the Z direction with respect to the first wall portion 21, the second wall portion 22, and the third wall portion 23.

A first light incident hole 2 a through which the measurement light L is incident into the casing 2 along the X direction is formed in the first wall portion 21. An inner surface 2 b parallel to both the X direction and the Z direction is formed in the third wall portion 23. Each of a plurality of positioning holes 2 c formed in the third wall portion 23 is open to the inner surface 2 b. The third wall portion 23 is integrally formed with the second support body 6. The main body portion 20 and the second support body 6 form a recessed portion 9 having the inner surface 2 b of the third wall portion 23 as a bottom surface 91. Namely, the casing 2 defines the recessed portion 9 having the inner surface 2 b of the third wall portion 23 as the bottom surface 91. The main body portion 20 and the second support body 6 are integrally formed from, for example, metal.

The casing 2 further includes a cover portion 25 and a shield cover 26. The cover portion 25 is attached to the main body portion 20 and the second support body 6 to close an opening of the recessed portion 9. The shield cover 26 is attached to the main body portion 20 and the cover portion 25 to cover the light detector 7 from the one side in the Z direction.

As illustrated in FIGS. 1 and 2 , the first support body 5 supports the plurality of beam splitters 3. Each of the beam splitters 3 has a plate shape and has a thickness of 1 mm or less. Each of the beam splitters 3 has a long shape when seen in a thickness direction of each of the beam splitters 3, and a direction perpendicular to a longitudinal direction of each of the beam splitters 3 is a direction parallel to the Y direction. The beam splitters 3 each have the same shape. Each of the beam splitters 3 has, for example, a rectangular plate shape.

The beam splitter 3 is formed, for example, by forming a dielectric multilayer film on the order of several nm, in which a plurality of layers of dielectric films each having a thickness of several Angstroms are stacked, on the surface of a glass layer having a thickness of approximately 0.5 to 1 mm. The refraction of light occurs even in the dielectric multilayer film, but when the difference in thickness between the glass layer and the dielectric multilayer film is taken into consideration, most of the refraction occurring in the beam splitter 3 occurs in the glass layer. In the present embodiment, the total thickness of the glass layer and the dielectric multilayer film is defined as the thickness of the beam splitter 3. A translucent material such as optical glass or plastic is used as the material of the beam splitter 3.

The first support body 5 is formed of a first wall portion 51, a second wall portion 52, a third wall portion 53, a fourth wall portion 54, and a fifth wall portion 55. The first wall portion 51 and the second wall portion 52 face each other in the X direction. The second wall portion 52 is located on the one side in the X direction with respect to the first wall portion 51. The third wall portion 53 and the fourth wall portion 54 face each other in the Y direction. The third wall portion 53 is located on the one side in the Y direction with respect to the first wall portion 51 and the second wall portion 52. The fourth wall portion 54 is located on the other side in the Y direction with respect to the first wall portion 51 and the second wall portion 52. The fifth wall portion 55 is located on the other side in the Z direction with respect to the first wall portion 51, the second wall portion 52, the third wall portion 53, and the fourth wall portion 54. The first support body 5 is integrally formed from, for example, metal.

A second light incident hole 5 a through which the measurement light L is incident on the plurality of beam splitters 3 along the X direction is formed in the first wall portion 51. An outer surface 5 b parallel to both the X direction and the Z direction is formed in the third wall portion 53. The outer surface 5 b is provided with a plurality of positioning pins 5 c. The first support body 5 is attached to the third wall portion 23 such that the outer surface 5 b is in contact with the inner surface 2 b of the casing 2 in a state where each of the positioning pins 5 c is fitted into each of the positioning holes 2 c of the casing 2, to define the position of the first support body 5 in a plane (along the plane) parallel to both the X direction and the Z direction.

The first support body 5 is disposed in the recessed portion 9 in a state where the outer surface 5 b is in contact with the inner surface 2 b of the casing 2 (namely, the bottom surface 91 of the recessed portion 9). A side surface 92 of the recessed portion 9 includes a plurality of separation regions 92 a. Each of the separation regions 92 a is separated from the first support body 5. In the present embodiment, the side surface 92 is formed of inner surfaces of the first wall portion 21, the second wall portion 22, and the fourth wall portion 24 of the main body portion 20 and a surface of the second support body 6, the surface being on the fourth wall portion 24 side. Incidentally, the side surface 92 may include at least one separation region 92 a. In addition, the separation region 92 a may be the entirety of the side surface 92.

A plurality of grooves 56 are formed in the first support body 5. Each of the beam splitters 3 is disposed in each of the grooves 56. Accordingly, the first support body 5 is provided with a plurality of combinations of the grooves 56 and the beam splitters 3. Hereinafter, each of the plurality of combinations is referred to as a “corresponding groove 56 and beam splitter 3”.

As illustrated in FIGS. 1 and 3 , each of the grooves 56 is open to an outer surface of the fifth wall portion 55. An extending direction of each of the grooves 56 is a direction parallel to the Y direction. A depth direction of each of the grooves 56 is a direction which is inclined by 45° such that the deeper the groove 56 is, the closer to the one side in the X direction the groove 56 is located, among directions perpendicular to the Y direction. Each of the grooves 56 has a pair of side surfaces 56 a and 56 b and a bottom surface 56 c. The pair of side surfaces 56 a and 56 b face each other in a width direction (direction perpendicular to both extending direction and the depth direction) of each of the grooves 56. A light passage opening 57 a is formed in the side surface 56 a and a light passage opening 57 b is formed in the side surface 56 b.

In the present embodiment, each of the grooves 56 is formed such that both end portions in the extending direction of the groove 56 are located in the third wall portion 53 and the fourth wall portion 54, respectively. The side surface 56 a is cut out by a space between the third wall portion 53 and the fourth wall portion 54 facing each other in the Y direction, so that the light passage opening 57 a is formed in the side surface 56 a. The side surface 56 b is cut out by the space, so that the light passage opening 57 b is formed in the side surface 56 b. In addition, the bottom surface 56 c is separated into two regions in the Y direction.

In the corresponding groove 56 and beam splitter 3, the groove 56 has a width (namely, a distance between the pair of the side surfaces 56 a and 56 b) twice or more the thickness of the beam splitter 3. As one example, the thickness of the beam splitter 3 is 0.5 mm, and the width of the groove 56 is 2.5 mm to 3.0 mm. In the corresponding groove 56 and beam splitter 3, the beam splitter 3 is disposed in the groove 56 so as to be in contact with the side surface 56 a and the bottom surface 56 c, the side surface 56 a being located on the one side of the pair of side surfaces 56 a and 56 b in the Z direction. In this state, the beam splitter 3 is fixed to the side surface 56 a and the bottom surface 56 c with, for example, adhesive agent.

As illustrated in FIG. 1 , in the spectroscopic module 1, a light incident portion 10 is formed of the first light incident hole 2 a and the second light incident hole 5 a. The light incident portion 10 defines light to be incident on the plurality of beam splitters 3 along the X direction. The second light incident hole 5 a includes the first light incident hole 2 a when seen in the X direction. In this case, a center line of the first light incident hole 2 a is an optical axis A of the light incident portion 10. As one example, when seen in the X direction, the first light incident hole 2 a has a circular shape, and the second light incident hole 5 a has an oval shape having the Z direction as a longitudinal direction. As one example, when seen in the X direction, the first light incident hole 2 a overlaps a portion on the one side in the Z direction of the second light incident hole 5 a. Accordingly, when the beam splitters 3 are disposed in the first support body 5, the centers of the beam splitters 3 can be confirmed through the first light incident hole 2 a and the second light incident hole 5 a.

As illustrated in FIGS. 4 and 5 , the second support body 6 supports the plurality of bandpass filters 4. Each of the bandpass filters 4 includes a light transmitting substrate 41, an interference film 42, and a light shielding film 43. The light transmitting substrate 41 has, for example, a rectangular plate shape. The interference film 42 is provided on a light incident surface 41 a of the light transmitting substrate 41. The interference film 42 is, for example, a dielectric multilayer film. The light shielding film 43 is provided on a side surface 41 b of the light transmitting substrate 41. The light shielding film 43 is, for example, a black paint film. In each of the bandpass filters 4, a surface on an opposite side of the interference film 42 from the light transmitting substrate 41 is a light incident surface 4 a of the bandpass filter 4, a surface on an opposite side of the light transmitting substrate 41 from the interference film 42 is a light outgoing surface 4 b of the bandpass filter 4, and an outer surface of the light shielding film 43 is a side surface 4 c of the bandpass filter 4. Incidentally, in FIGS. 1 and 2 , each of the bandpass filters 4 is illustrated in a state where the configuration is simplified.

The second support body 6 includes a support portion 61. A support surface 61 a is formed in the support portion 61 so as to be open to the one side in the Z direction. The fact that the support surface 61 a is open to the one side in the Z direction means that when the support portion 61 is seen from the one side in the Z direction in a state where there is only the second support body 6, the support surface 61 a is exposed (namely, that the support surface 61 a is visible). The plurality of bandpass filters 4 are disposed on the support surface 61 a to be arranged along the X direction. The support surface 61 a is a surface perpendicular to the Z direction, and is formed in the support portion 61 such that a region on the light incident surface 4 a of each of the bandpass filters 4 is in contact with the support surface 61 a, the region being located outside a clear aperture 40. The clear aperture 40 is an effective opening region in which the function of the bandpass filter 4 is guaranteed. One light passage opening 61 b through which a plurality of optical paths (dotted line illustrated in FIG. 1 ) from the plurality of beam splitters 3 to the plurality of bandpass filters 4 pass is formed in the support portion 61. Accordingly, the support surface 61 a is separated into two regions in the Y direction.

The second support body 6 further includes a restriction portion 62. The restriction portion 62 is provided in the second support body 6 so as to be located on the one side in the Z direction with respect to the support portion 61. The restriction portion 62 restricts each of the bandpass filters 4 from moving in a direction perpendicular to the Z direction. The restriction portion 62 is formed of a plurality of contact portions 62 a that are provided so as to be in contact with the side surface 4 c of each of the bandpass filters 4, and a plurality of separation portions 62 b that are provided so as to be separated from the side surface 4 c of each of the bandpass filters 4. The restriction portion 62 does not completely partition the plurality of bandpass filters 4 off from each other. Namely, the plurality of bandpass filters 4 are separated from each other with a space interposed therebetween in a state where the movement thereof in the direction perpendicular to the Z direction is restricted by the restriction portion 62.

As illustrated in FIGS. 1 and 2 , a recessed portion 63 which is open to the one side in the Z direction is formed in the second support body 6. A bottom surface 63 a of the recessed portion 63 is a surface on an opposite side of the restriction portion 62 from the support portion 61. The distance between the support surface 61 a and the bottom surface 63 a in the Z direction is smaller than the thickness of each of the bandpass filters 4 (namely, a distance between the light incident surface 4 a and the light outgoing surface 4 b in the Z direction). Accordingly, a portion on an opposite side of each of the bandpass filters 4 from the support portion 61 protrudes from the bottom surface 63 a, and the light outgoing surface 4 b of each of the bandpass filters 4 is located on the one side in the Z direction from the bottom surface 63 a (refer to FIG. 4 ). The bottom surface 63 a is provided with a plurality of positioning pins 6 a.

As illustrated in FIGS. 1 and 2 , the light detector 7 includes a wiring substrate 71, a plurality of light detection elements 72, and a connector 73. The plurality of light detection elements 72 are mounted on a surface 71 a to be arranged along the X direction, the surface 71 a being on a plurality of bandpass filters 4 side of the wiring substrate 71. Each of the light detection elements 72 is a discrete semiconductor element such as a PD chip, and has the light receiving region 7 a. The connector 73 is attached to a surface 71 b, the surface 71 b being on an opposite side of the wiring substrate 71 from the surface 71 a. The connector 73 is a port through which an electric signal or the like is input to and output from each of the light detection elements 72. The connector 73 extends outside the casing 2 through an opening 26 a formed in the shield cover 26. The light detector 7 is attached to the second support body 6 so as to close an opening of the recessed portion 63. In the present embodiment, the wiring substrate 71 is attached to the second support body 6 to close the opening of the recessed portion 63, and the plurality of light detection elements 72 are disposed in the recessed portion 63.

The light shielding member 8 is disposed between the plurality of bandpass filters 4 and the light detector 7. The light shielding member 8 is made of an elastic material, and is disposed in the recessed portion 63 of the second support body 6 in a state where the light shielding member 8 is compressed. In this state, the plurality of bandpass filters 4 are held between the support portion 61 of the second support body 6 and the light shielding member 8. A plurality of light passage openings 8 a are formed in the light shielding member 8. Each of a plurality of optical paths from the plurality of bandpass filters 4 to the plurality of light receiving regions 7 a passes through each of the plurality of light passage openings 8 a. Namely, the plurality of optical paths from the plurality of bandpass filters 4 to the plurality of light receiving regions 7 a are separated from each other by the light shielding member 8. In the present embodiment, each of the light detection elements 72 of the light detector 7 is located inside each of the light passage openings 8 a of the light shielding member 8. In each of the light passage openings 8 a, a terminal of the light detection element 72 and a terminal of the wiring substrate 71 are electrically connected by a wire 74, and the wire 74 is covered with a resin member 75.

As illustrated in FIG. 6 , each of the light passage openings 8 a is formed in the light shielding member 8 such that a region on the light outgoing surface 4 b of each of the bandpass filters 4 is in contact with the light shielding member 8, the region being located outside the clear aperture 40. Namely, the light shielding member 8 is formed such that a region on the light outgoing surface 4 b of each of the bandpass filters 4 is in contact with the light shielding member 8, the region being located outside the clear aperture 40. Incidentally, in FIG. 6 , the bandpass filter 4 is illustrated with an alternate long and two short dashes line.

As illustrated in FIG. 2 , a plurality of positioning holes 8 b are formed in the light shielding member 8. A plurality of positioning holes 7 b are formed in the wiring substrate 71. Each of the positioning holes 7 b overlaps each of the positioning holes 8 b when seen in the Z direction. The light shielding member 8 is disposed in the recessed portion 63 in a state where each of the positioning pins 6 a of the second support body 6 is fitted into each of the positioning holes 8 b, to define the position of each of the light passage openings 8 a in the direction perpendicular to the Z direction. The light detector 7 is attached to the second support body 6 in a state where each of the positioning pins 6 a which has penetrated through the positioning hole 8 b of the light shielding member 8 is fitted into each of the positioning holes 7 b, to define the position of each of the light receiving regions 7 a in the direction perpendicular to the Z direction.

As illustrated in FIG. 7 , the plurality of beam splitters 3 are disposed such that a center 3 a of each of the beam splitters 3 is located on a line α parallel to the X direction. The center 3 a of the beam splitter 3 is the center (center of gravity) of the beam splitter 3 when seen in the thickness direction of the beam splitter 3. The beam splitters 3 each have the same thickness of 1 mm or less, and are disposed such that light is incident at an angle of incidence of 45° along the X direction. The optical axis A of the light incident portion 10 is located on the one side in the Z direction with respect to the line α passing through the center 3 a of each of the beam splitters 3. Incidentally, in FIG. 7 , the light incident portion 10 is schematically illustrated.

Since refraction of light occurs in each of the beam splitters 3, the optical axis of transmitted light is shifted to a side away from the optical axis A of the light incident portion 10 with respect to the optical axis of incident light. In the spectroscopic module 1, since the beam splitters 3 each have the same thickness and the beam splitters 3 each are disposed such that light is incident at an angle of incidence of 45° along the X direction, the beam splitters 3 each have the same amount of light refraction. The amount of light refraction means an amount by which the optical axis of the transmitted light is shifted to the side away from the optical axis A of the light incident portion 10 with respect to the optical axis of the incident light in the beam splitter 3.

When the amount of light refraction in each of the beam splitters 3 is ΔZ and the number of the beam splitters 3 is M, the distance between “the optical axis of light incident on the beam splitter 3 of the foremost stage” and “the optical axis of light incident on the beam splitter 3 of the rearmost stage” in the Z direction is ΔZ(M−1). The beam splitter 3 of the foremost stage means the beam splitter 3 disposed in the foremost stage (on an upstream side in a traveling direction of light), and the beam splitter 3 of the rearmost stage means the beam splitter 3 disposed in the rearmost stage (on a downstream side in the traveling direction of light).

In the spectroscopic module 1, the plurality of beam splitters 3 are disposed with respect to the optical axis A of the light incident portion 10 such that the distance between the optical axis A and the line α in the Z direction is ΔZ(M−1)/2. Accordingly, in the beam splitter 3 disposed in a middle stage (on a midstream side in the traveling direction of light), the optical axis of incident light passes through the center 3 a or the vicinity of the center 3 a of the beam splitter 3.

As one example, when the thickness of each of the beam splitters 3 is 0.5 mm, the refractive index is 1.5, the angle of incidence to the beam splitter 3 is 45°, and the number of the beam splitters 3 disposed is 10, the value of an amount ΔZ of light refraction is 0.165 mm. Therefore, the distance between the optical axis A and the line α in the Z direction is ΔZ(M−1)/2=0.165×(10−1)/2=approximately 0.74 mm. In this case, in each of the beam splitters 3 of a fifth stage and a sixth stage from the foremost stage, the optical axis of incident light passes through the vicinity of the center 3 a of the beam splitter 3. When the diameter of the measurement light L which is defined by the light incident portion 10 (namely, the diameter of light incident on the beam splitter 3 of the foremost stage) is 4 mm, if the length in the longitudinal direction of each of the beam splitters 3 is 10 mm, the incident light is contained in the clear apertures in all the beam splitters 3.

In the spectroscopic module 1, the arrangement pitch of the plurality of beam splitters 3 is a value obtained by adding the amount of light refraction in each of the beam splitters 3 to the arrangement pitch of the plurality of light receiving regions 7 a. The arrangement pitch of the plurality of beam splitters 3 means “a distance between the centers 3 a of the beam splitters 3 adjacent to each other” when the plurality of beam splitters 3 are arranged at equal intervals along the X direction. The arrangement pitch of the plurality of light receiving regions 7 a means “a distance between the centers of the light receiving regions 7 a adjacent to each other” when the plurality of light receiving regions 7 a are arranged at equal intervals along the X direction. When the arrangement pitch of the plurality of beam splitters 3 is P1 and the arrangement pitch of the plurality of light receiving regions 7 a is P2, P1=P2+ΔZ. Therefore, when the number of the beam splitters 3 is M, the distance between “the beam splitter 3 of the foremost stage” and “the beam splitter 3 of the rearmost stage” in the X direction is P1(M−1)=(P2+ΔZ)(M−1)=P2(M−1)+ΔZ(M−1). As described above, the arrangement pitch of the plurality of beam splitters 3 is cumulatively affected by not only the arrangement pitch of the plurality of light receiving regions 7 a but also the amount of light refraction in each of the beam splitters 3.

From the above viewpoint, “in the entirety of the plurality of beam splitters 3, the total accumulated amount of light refraction is sufficiently reduced on the side away from the bandpass filters 4 and on a rear stage side in a direction in which the plurality of beam splitters 3 are lined up, so that the size of the entirety of the module is reduced”, each of the beam splitters 3 preferably has a thickness of 1 mm or less, and more preferably has a thickness of 0.5 mm or less. However, from the viewpoint that the strength of the beam splitter 3 is secured, it is preferable that each of the beam splitters 3 has a thickness of 0.1 mm or more.

In the spectroscopic module 1, each of the beam splitters 3 has a plate shape and has a thickness of 1 mm or less. Accordingly, in each of the beam splitters 3, the amount by which the optical axis of the transmitted light is shifted to the side away from the bandpass filter 4 with respect to the optical axis of the incident light (the amount of light refraction) is reduced. Therefore, in the entirety of the plurality of beam splitters 3, the total accumulated amount of light refraction is sufficiently reduced not only on the side away from the bandpass filter 4 but also on the rear stage side in a direction in which the plurality of beam splitters 3 are lined up (X direction). The fact that the total accumulated amount of light refraction is reduced means that the optical path length of the optical path to the light receiving region 7 a other than the light receiving region 7 a disposed in the foremost stage among the plurality of light receiving regions 7 a is suppressed from being increased. Accordingly, a reduction in amount of received light in the light receiving region 7 a and the generation of stray light in the optical path can be suppressed. As a result, in the spectroscopic module 1, the S/N ratio can be improved. Specifically, since the optical path length of the optical path is suppressed from being increased, and the amount of received light in the light receiving region 7 a in a rear stage is suppressed from being reduced, the amplification factor of an electric signal in a circuit of the wiring substrate 71 can be suppressed. In addition, since the optical path length of the optical path is suppressed from being increased, diffuse reflection, scattering, or the like of light in the optical path can be suppressed. Therefore, the generation of stray light in the optical path can be suppressed. In addition, according to the spectroscopic module 1, in the entirety of the plurality of beam splitters 3, the total accumulated amount of light refraction is sufficiently reduced not only on the side away from the bandpass filter 4 but also on the rear stage side in the direction in which the plurality of beam splitters 3 are lined up (X direction). Therefore, the size of the entirety of the module can be reduced.

In addition, when each of the beam splitters 3 has a thickness of 0.5 mm or less, the optical path length of the optical path to the light receiving region 7 a in a rear stage is further suppressed from being increased. Therefore, the S/N ratio of the entirety of the spectroscopic module 1 can be even further improved. Further, in the spectroscopic module 1, the size of the entirety of the module can be even further reduced.

In addition, in the spectroscopic module 1, each of the beam splitters 3 has a plate shape and is disposed in each of the grooves 56 formed in the first support body 5, and in the corresponding groove 56 and beam splitter 3, the groove 56 has a width twice or more the thickness of the beam splitter 3. Accordingly, during production of the spectroscopic module 1, the groove 56 in which the beam splitter 3 is disposed can be easily and accurately formed. Therefore, the positional accuracy of each of the beam splitters 3 can be secured. For example, when the groove 56 is formed in the first support body 5 by using an end mill, a tip of the end mill is suppressed from being shaken during processing. Therefore, the groove 56 can be easily and accurately formed in the first support body 5.

In addition, in the spectroscopic module 1, in the corresponding groove 56 and beam splitter 3, the beam splitter 3 is disposed in the groove 56 so as to be in contact with the side surface 56 a of the pair of side surfaces 56 a and 56 b and the bottom surface 56 c, the side surface 56 a being located on the one side in the Z direction. Accordingly, in addition to securing the positional accuracy of each of the beam splitters 3, each of the plurality of beam splitters 3 can be stably supported.

In addition, in the spectroscopic module 1, the plurality of beam splitters 3 are disposed such that the center 3 a of each of the beam splitters 3 is located on the line α parallel to the X direction, and the optical axis A of the light incident portion 10, which defines light to be incident on the plurality of beam splitters 3 along the X direction, is located on the one side in the Z direction with respect to the line α. Accordingly, the clear aperture of each of the beam splitters 3 can be effectively utilized while the size of the beam splitters 3 each having the same size is reduced.

In addition, in the spectroscopic module 1, the beam splitters 3 each have the same thickness and are disposed such that light is incident at an angle of incidence of 45° along the X direction, and the arrangement pitch of the plurality of beam splitters 3 is a value obtained by adding the amount of light refraction in each of the beam splitters 3 to the arrangement pitch of the plurality of light receiving regions 7 a. Accordingly, light reflected by the beam splitters 3 can be accurately incident on the light receiving regions 7 a. In addition, in the spectroscopic module 1, P1 which is the arrangement pitch of the plurality of beam splitters 3 is constant (P1=P2+ΔZ). Accordingly, the arrangement pitch between the plurality of light receiving regions 7 a adjacent to each other in the X direction can be constant, so that production can be facilitated.

In addition, in the spectroscopic module 1, each of the beam splitters 3 has a long shape when seen in the thickness direction of each of the beam splitters 3, and a direction perpendicular to the longitudinal direction of each of the beam splitters 3 is the Y direction (direction perpendicular to both the X direction and the Z direction). Accordingly, the clear aperture of each of the beam splitters 3 can be effectively utilized while the size of each of the beam splitters 3 in the Y direction is reduced. In addition, in the Y direction, the size of each of the beam splitters 3 is reduced, so that the size of the casing 2 can be also reduced.

In addition, in the spectroscopic module 1, each of the beam splitters 3 has the same shape. Accordingly, the components can be common to the plurality of beam splitters 3.

The present disclosure is not limited to the above embodiment. For example, in the embodiment, the plurality of beam splitters 3 are arranged along the first direction (X direction), and the plurality of bandpass filters 4 and the like are disposed on the one side in the second direction (Z direction) with respect to the plurality of beam splitters 3. Namely, in the above embodiment, the second direction (Z direction) is a direction perpendicular to the first direction (X direction); however, the second direction may be a direction intersecting the first direction. In addition, in the above embodiment, the meaning of “to be in contact with” is not limited to a case where a member and a member are in contact with each other, and includes a case where a film such as adhesive agent is disposed between a member and a member.

In addition, the casing 2 may accommodate at least the plurality of beam splitters 3 and the plurality of bandpass filters 4. In addition, a portion of the casing 2 may be formed of a portion of at least one of the first support body 5, the second support body 6, and the light detector 7. In addition, the first support body 5 and the second support body 6 may be integrally formed. In addition, the light outgoing surface 4 b of each of the bandpass filters 4 is located on the one side in the Z direction from the bottom surface 63 a of the recessed portion 63 in which the light shielding member 8 is disposed, but may be located at the same position as that of the bottom surface 63 a.

In addition, each of the beam splitters 3 may be a dichroic mirror that reflects light in different wavelength bands and transmits light other than the light in the reflected wavelength bands. In addition, as long as each of the beam splitters 3 has a long shape when seen in the thickness direction of each of the beam splitters 3, each of the beam splitters 3 may have a polygonal shape, an elliptical shape, or the like as a specific shape. In addition, the plurality of bandpass filters 4 may be formed, for example, by forming at least two dielectric multilayer films on one preform. Namely, a plurality of portions, each of which functions as the bandpass filter 4, may be provided, and the preform on which each of the plurality of portions is disposed is not required to be divided. In addition, the light detector 7 may be a PD array or the like in which the plurality of light receiving regions 7 a are formed on one semiconductor substrate. In addition, the light detector 7 may be a photomultiplier tube.

In addition, in the above embodiment, the casing 2 includes the plurality of positioning holes 2 c as a defining portion; however, at least one of the second support body 6 and the casing 2 may include a defining portion that defines the position of the first support body 5 in a plane parallel to both the X direction and the Z direction. The defining portion provided in the second support body 6 and the casing 2 may be, for example, a contact region that is provided in the side surface 92 of the recessed portion 9 so as to be in contact with the first support body 5, the first support body 5 disposed in the recessed portion 9. In addition, the first support body 5 may include a first engagement portion, and the casing 2 may include a second engagement portion engaged with the first engagement portion, as the defining portion. In that case, one of the first engagement portion and the second engagement portion may be formed of a plurality of positioning holes, and the other of the first engagement portion and the second engagement portion may be formed of positioning pins, each of the positioning pins fitted into each of the plurality of positioning holes.

In addition, in the above embodiment, the second support body 6 includes the positioning pins 6 a, and the light shielding member 8 includes the positioning holes 8 b; however, the second support body 6 may include a first engagement portion, and the light shielding member 8 may include a second engagement portion engaged with the first engagement portion. In that case, one of the first engagement portion and the second engagement portion may be formed of a plurality of positioning holes o, and the other of the first engagement portion and the second engagement portion may be formed of positioning pins, each of the positioning pins fitted into each of the plurality of positioning holes.

In addition, when the beam splitter 3 has a plate shape and has a thickness of 1 mm or less (more preferably, a thickness of 0.5 mm or less), if the number of all the beam splitters 3 is M (M is a natural number of 2 or more), each of N (N is a natural number of 2 to M) beam splitters 3 among M beam splitters 3 may have a plate shape and have a thickness of 1 mm or less (more preferably, a thickness of 0.5 mm or less). Incidentally, all the beam splitters 3 each may have a plate shape and have a thickness of 1 mm or less (more preferably, a thickness of 0.5 mm or less) (the case of M=N).

According to one aspect of the present disclosure, there is provided a spectroscopic module including: M beam splitters that are arranged along a first direction, where M is a natural number of 2 or more; M bandpass filters that are disposed on one side in a second direction intersecting the first direction with respect to the M beam splitters, each of the M bandpass filters facing each of the M beam splitters; a light detector that is disposed on the one side in the second direction with respect to the M bandpass filters and includes M light receiving regions, each of the M light receiving regions facing each of the M bandpass filters; and a support body that supports the M beam splitters and the M bandpass filters. Each of N beam splitters among the M beam splitters has a plate shape and has a thickness of 1 mm or less, where N is a natural number of 2 to M.

In the spectroscopic module, each of the N beam splitters among the M beam splitters has a plate shape and has a thickness of 1 mm or less. Accordingly, in each of the N beam splitters, the amount by which the optical axis of transmitted light is shifted to a side away from the bandpass filter with respect to the optical axis of incident light (the amount of light refraction) is reduced. Therefore, in the entirety of the N beam splitters, the total accumulated amount of light refraction is sufficiently reduced not only on the side away from the bandpass filter but also on a rear stage side in a direction in which the N beam splitters are lined up. The fact that the total accumulated amount of light refraction is reduced means that the optical path length of the optical path to the light receiving region other than the light receiving region disposed in the foremost stage among the plurality of light receiving regions is suppressed from being increased. Accordingly, a reduction in amount of received light in the light receiving region and the generation of stray light in the optical path can be suppressed. As a result, according to the spectroscopic module, the S/N ratio can be improved.

In the spectroscopic module according to one aspect of the present disclosure, each of the N beam splitters may have a thickness of 0.5 mm or less. Accordingly, the optical path length of the optical path to the light receiving region other than the light receiving region disposed in the foremost stage among the plurality of light receiving regions is further suppressed from being increased. Therefore, the S/N ratio of the entirety of the module can be even further improved.

In the spectroscopic module according to one aspect of the present disclosure, the support body may include a support portion in which N grooves are formed. Each of the N beam splitters may be disposed in each of the N grooves so that the support portion is provided with N combinations each including a groove and a beam splitter. In each of the N combinations, the groove may have a width twice or more a thickness of the beam splitter. Accordingly, during production of the spectroscopic module, the groove in which the beam splitter is disposed can be easily and accurately formed. Therefore, the positional accuracy of each of the N beam splitters can be secured.

In the spectroscopic module according to one aspect of the present disclosure, in each of the N combinations, the groove may have a pair of side surfaces each having a light passage opening therein, and a bottom surface. In each of the N combinations, the beam splitter may be disposed in the groove so as to be in contact with a side surface of the pair of side surfaces and the bottom surface, the side surface being located on the one side in the second direction. Accordingly, in addition to securing the positional accuracy of each of the N beam splitters, each of the N beam splitters can be stably supported.

The spectroscopic module according to one aspect of the present disclosure may further include a light incident portion that defines light to be incident on the M beam splitters along the first direction. The N beam splitters may be supported by the support body such that a center of each of the N beam splitters is located on a line parallel to the first direction. An optical axis of the light incident portion may be located on the one side in the second direction with respect to the line. Accordingly, for example, when each of the N beam splitters has the same shape, a clear aperture of each of the N beam splitters can be effectively utilized while the size of each of the N beam splitters is reduced.

In the spectroscopic module according to one aspect of the present disclosure, the N beam splitters each may have the same thickness, and be disposed such that light is incident at an angle of incidence of 45° along the first direction. An arrangement pitch of the N beam splitters may be a value obtained by adding an amount of light refraction in each of the N beam splitters to an arrangement pitch of N light receiving regions corresponding to the N beam splitters among the M light receiving regions. Accordingly, light reflected by the N beam splitters can be accurately incident on the N light receiving regions.

In the spectroscopic module according to one aspect of the present disclosure, each of the N beam splitters may have a long shape when seen in a thickness direction of each of the N beam splitters. A direction perpendicular to a longitudinal direction of each of the N beam splitters may be a direction perpendicular to both the first direction and the second direction. Accordingly, in the direction perpendicular to both the first direction and the second direction, the clear aperture of each of the N beam splitters can be effectively utilized while the size of each of the N beam splitters is reduced.

In the spectroscopic module according to one aspect of the present disclosure, each of the N beam splitters may have the same shape. Accordingly, the components can be common to the N beam splitters. 

What is claimed is:
 1. A spectroscopic module comprising: a plurality of beam splitters that are arranged along a first direction; a plurality of bandpass filters that are disposed on one side in a second direction intersecting the first direction with respect to the plurality of beam splitters and face the plurality of beam splitters; and a light detector that is disposed on the one side in the second direction with respect to the plurality of bandpass filters and includes a plurality of light receiving regions facing the plurality of bandpass filters, wherein each of the plurality of beam splitters has a plate shape and has a thickness of 0.5 mm or more and 1 mm or less.
 2. The spectroscopic module according to claim 1, wherein an amount of light refraction of each of the plurality of beam splitters is 0.165 mm or more.
 3. The spectroscopic module according to claim 1, wherein an arrangement pitch of the plurality of beam splitters in the first direction is constant.
 4. The spectroscopic module according to claim 1, further comprising a support body that supports the plurality of beam splitters, wherein the support body is formed from metal.
 5. The spectroscopic module according to claim 1, further comprising a support body that supports the plurality of beam splitters, wherein the support body has a plurality of support surfaces arranged along the first direction and supporting the plurality of beam splitters, the support body includes a wall portion connected to the plurality of support surfaces and being parallel to both the first direction and the second direction, and when seen in the first direction, a thickness of the wall portion in a third direction intersecting both the first direction and the second direction is smaller than a thickness of each of the plurality of bandpass filters in the second direction.
 6. The spectroscopic module according to claim 1, wherein when seen in the first direction, a width of each of the plurality of beam splitters in the second direction is larger than a thickness of each of the plurality of bandpass filters in the second direction.
 7. The spectroscopic module according to claim 1, further comprising a casing that accommodates the plurality of beam splitters, wherein a light incident hole through which a measurement light is incident into the casing along the first direction is formed in the casing, and when seen in a third direction intersecting both the first direction and the second direction, a width of the light incident hole in the second direction is smaller than a length of each of the plurality of beam splitters in a direction perpendicular to a thickness direction thereof.
 8. The spectroscopic module according to claim 1, further comprising a casing that accommodates the plurality of beam splitters, wherein a light incident hole through which a measurement light is incident into the casing along the first direction is formed in the casing, and when seen in the first direction, a center of the light incident hole is located on the one side in the second direction with respect to a center of a beam splitter closest to the light incident hole among the plurality of beam splitters. 